CODEWITHSUNDEEP
javabuttonjavafx
FatFockFrank
FatFockFrank

Reputation: 169

How would I add an action listener to buttons on a loop?

I want it so every time a button is pressed in my 4x4 grid, that it increments moves by 1 . This is creating a 4x4 layout of buttons. Each time any of those buttons are pressed, I want moves to increment. Basically I'm creating the memory game, where you flip cards over to match each other. I just have to keep count of the total amount of moves a player does to solve the puzzle.

private int moves = 0;

private GridPane makeGridPane(){
    ConcentrationModel c = new ConcentrationModel();
    GridPane grid = new GridPane();

    ColumnConstraints col1 = new ColumnConstraints();
    col1.setPercentWidth( 50 );

    grid.getColumnConstraints().addAll(col1, col1, col1, col1);
    RowConstraints row1 = new RowConstraints();
    row1.setPercentHeight( 50 );
    grid.getRowConstraints().addAll(row1, row1, row1, row1);


    for(int row = 0; row < 4; row ++){
        for(int col = 0; col < 4; col++){
            Button btn = new Button();
            ImageView image = new ImageView(c.getCards().get(0).getImage());
            image.setFitWidth(WIDTH/4);
            image.setFitHeight(HEIGHT/4);
            btn.setMaxSize(Double.MAX_VALUE, Double.MAX_VALUE);
            btn.setGraphic(image);
            grid.add(btn, col, row);


        }
    }
    return grid;
}

Upvotes: 0

Views: 3413

Answers (3)

anon
anon

Reputation:

This is actually pretty simple. All you have to do is add this bit of code just before your grid.add(...):

btn.setOnAction(new EventHandler<ActionEvent>() {
    @Override public void handle(ActionEvent event) {
        moves++;
    }
});

Or, equivalently, the Java 8 version:

btn.setOnAction((ActionEvent e) -> {moves++;});

(I can't currently test this, but it should work. If not, lemme know and I'll try to fix it.)

If you're concerned about memory, Christian points out below that this creates a new instance of EventHandler for every button. While this may not be too terrible, it's probably a bad habit to get into. The best way to handle (no pun intended) this is by making an object before your for loop:

EventHandler<ActionEvent> eh = new EventHandler<>() {
    @Override public void handle(ActionEvent event) {
        moves++;
    }
};

Then, for each of your buttons, instead of the top-most code, you'd simply write:

btn.setOnAction(eh);

That way, a single EventHandler is being created and used to handle all the events. You'll want to use this one if you need to create more than just a few buttons, both because it's faster (doesn't need to allocate memory for each object) and more memory-efficient (...it, uh, doesn't need to allocate the memory for each object). In this case, I think it's pretty trivial, but it's good to know nonetheless.

Upvotes: 1

James_D
James_D

Reputation: 209225

You can create a single event handler and reuse it for all the buttons. Since you probably want the buttons to do other things too, I would recommend adding this as an event handler, instead of using the convenience method setOnAction(...):

EventHandler<ActionEvent> incrementMovesHandler = e -> moves++ ;

for(int row = 0; row < 4; row ++){
    for(int col = 0; col < 4; col++){
        Button btn = new Button();
        btn.addEventHandler(ActionEvent.ACTION, incrementMovesHandler);
        // ...
    }
}

Upvotes: 2

Christian Abella
Christian Abella

Reputation: 5797

You need to implement the ActionListener interface in your class. Then in the actionPerformed function, just increment the moves variable. You just have to call btn.addActionListener(this); for each of the button that you created.

public class Sample extends JFrame implements ActionListener {

  public Sample ()
  {

  }


  private GridPane makeGridPane()
  {
    ConcentrationModel c = new ConcentrationModel();
    GridPane grid = new GridPane();

    ColumnConstraints col1 = new ColumnConstraints();
    col1.setPercentWidth( 50 );

    grid.getColumnConstraints().addAll(col1, col1, col1, col1);
    RowConstraints row1 = new RowConstraints();
    row1.setPercentHeight( 50 );
    grid.getRowConstraints().addAll(row1, row1, row1, row1);


    for(int row = 0; row < 4; row ++){
        for(int col = 0; col < 4; col++){
            Button btn = new Button();
            ImageView image = new ImageView(c.getCards().get(0).getImage());
            image.setFitWidth(WIDTH/4);
            image.setFitHeight(HEIGHT/4);
            btn.setMaxSize(Double.MAX_VALUE, Double.MAX_VALUE);
            btn.setGraphic(image);
            btn.addActionListener(this);
            grid.add(btn, col, row);


        }
    }
    return grid;
  }


  public void actionPerformed(ActionEvent e) 
  {
    moves++;
  }  

}

Upvotes: -2

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